The present invention relates to a vehicle seat and, more particularly, to a vehicle seat having a mechanism for moving a headrest when a rear end collision occurs.
When a motor vehicle undergoes a collision from the vehicle rear side, that is, when an rear end collision occurs, the head of a passenger seated on a vehicle seat is moved suddenly to the rear by inertia, so that the neck and other parts of the passenger may undergo a shock. Conventionally, therefore, a known vehicle seat has a configuration for supporting the passenger's head and easing a shock by moving a headrest forward when a rear end collision occurs in order to protect the passenger's head, neck, and other parts from the shock at the rear end collision time, as is disclosed, e.g., in Japanese Unexamined Patent Application Publication No. 2006-182094 (“the '094 Publication”).
The vehicle seat described in the '094 Publication is configured so that a plate body is installed to a seat back frame so as to be movable back and forth; a headrest is installed to the upper part of the seat back frame so as to be movable back and forth by an upper link; a lower link is installed to the lower part of the seat back frame so as to be turnable; and the lower link and the upper link are connected to each other by a transmission member (connecting link). With this design, a load sensed by the plate body when a rear end collision occurs is transmitted to the upper-side link to move the headrest forward.
For the vehicle seat described in the '094 Publication, a load at the time when the passenger is moved rearward by the rear end collision is received at the vicinity of the waist at which the rearward displacement is larger than at the back, so that the rear end collision can be sensed with certainty. Also, by the configuration such that a load received by the plate body is transmitted to the upper link via the lower link and the transmission member (connecting link), the load can be transmitted to the upper link with high transmission efficiency, so that the operation of forward movement of the headrest is reliable.
However, for the vehicle seat described in the '094 Publication described above, as shown in the transverse sectional view of FIG. 8, there is a portion in which a connecting link 140 for connecting the lower link and the upper link to each other is arranged so as to project significantly to the backrest surface side from a side frame 121. Therefore, if the vehicle seat is manufactured as a thin type, the thickness t2 of a cushion material 104 of a portion arranged on the backrest surface side of the side frame 121 decreases, which presents a problem in that it is difficult to keep the seating comfortable.